The present invention relates to the field of medical devices, and, more particularly, to spinal implants and related methods.
A normal human spine has two curves called the kyphotic curve and the lordotic curve. The kyphotic curve is the outward curve of the thoracic vertebrae (at the level of the ribs). The lordotic curve is the inward curve of the lumbar vertebrae (just above the buttocks).
A small degree of both kyphotic and lordotic curvature is normal, but in some circumstances these curves may become exaggerated. Exaggeration of the kyphotic curve is called Scheuermann""s disease, and this condition results in rounded or hunched shoulders. Exaggeration of the lordotic curve is called lordosis, or more commonly xe2x80x9cswayback.xe2x80x9d Depending upon the severity of the case, medical (i.e., surgical) intervention is sometimes required to correct the abnormal curvature associated with Scheuermann""s disease and lordosis. Similarly, medical intervention is frequently required for a third type of scoliotic or sideways curvature of the spine called scoliosis.
To this end, numerous types of spinal implant devices have been developed to correct or modify an angle of spinal curvature. For example, U.S. Pat. No. 6,277,149 to Boyle et al. discloses a ramp-shaped intervertebral implant formed from the diaphysis or metaphysis of a long bone or other biocompatible material. The implant may also have ridges defined on top and bottom surfaces thereof to help hold the implant in place. Additionally, perforations may be formed along any of the surfaces of the implant to facilitate bone ingrowth.
Another similar implant is disclosed in U.S. Pat. No. 6,302,914 to Michelson, which also has serrations for holding the insert in place as well as holes to allow bone in-growth. Other examples of wedge-shaped or tapered implants are disclosed in U.S. Pat. Nos. 6,045,580 and 6,315,795 both to Scarborough et al.; U.S. Pat. No. 5,984,922 to McKay; and U.S. Pat. No. 6,117,174 to Nolan; and in Published Application Nos. 2001/0031965 to Zucherman et al. and 2001/0008980 to Gresser et al. Each of these implants is designed to be used in pairs, i.e., one is to be inserted on each side of the center of the spine between two vertebral bodies so that both halves of the spine are supported.
While the above devices may be effective for correcting spinal curvature, their insertion may in some instances be quite obtrusive to the patient. That is, to insert two implants between vertebral bodies may require more than one incision by the surgeon as well as movement of several back muscles, ligaments, etc. As a result, significant trauma may be experienced by the patient, which can not only increase his pain but also prolong recovery. Additionally, using multiple spinal implants may be expensive, and they may require a relatively long time for a surgeon to insert in a patient.
In view of the foregoing background, it is therefore an object of the present invention to provide an intervertebral support device which provides correction for conditions such as lordosis, Scheuermann""s disease, and scoliosis, while causing less trauma to a patient during implantation.
This and other objects, features, and advantages in accordance with the present invention are provided by an intervertebral support device for providing a corrected angle of spinal curvature upon positioning between adjacent vertebral bodies of a human spine. The intervertebral support device may include a body having opposing first and second end faces, opposing top and bottom faces extending between the first and second end faces, and opposing side faces extending between the first and second end faces. Furthermore, a first diagonal direction may be defined between a first vertical corner at the first end face and a diagonally opposite second vertical corner at the second end face, and a second diagonal direction defined between a second vertical corner at the first end face and a diagonally opposite first vertical corner at the second end face.
As such, in certain embodiments the body may have a tapering height decreasing from the first end face to the second end face, and while also tapering more quickly in the first diagonal direction than the second diagonal direction. The intervertebral support device thereby provides the corrected angle of spinal curvature upon positioning between adjacent vertebral bodies of the human spine. In other embodiments, the body may alternately (or in addition) have an axis, and the opposing first and second end faces may be canted at respective angles from perpendicular to the axis of the body to thereby provide the corrected angle of spinal curvature upon positioning between adjacent vertebral bodies of the human spine. By way of example, the body may be generally rectangular in shape.
More particularly, the first and second end faces may be canted at greater than about 10xc2x0 from perpendicular to the axis of the body. Further, the respective angles of canting of the first and second end faces may be substantially equal. Also, the body may further include opposing side faces, and the body may have one or more spikes and/or serrations defined on at least one of the top, bottom, and side faces. The body may further have at least one cavity defined therein for vertebral bone ingrowth.
The tapered height may define a taper angle less than about 10xc2x0 from the first end face to the second end face, and, more preferably, in a range of about 3-5xc2x0. Also, edge portions of at least one of the first and second end faces may be rounded over. In certain embodiments, the body may be hollow, and it may also have a support therein for supporting at least one of the sides. The body may also be a skeletal frame, and it may include at least one of bone, metal, carbon fiber, and PEAK, for example.
A method aspect of the invention is for providing a corrected angle of curvature to a spine in a human patient. The method may include positioning an intervertebral support device, such as the one described briefly above, between adjacent vertebral bodies in the spine and transverse to an imaginary vertical plane bisecting the spine and normal to the posterior thereof to thereby provide the corrected angle of spinal curvature. As such, only a single support device need be used to provide support to both sides of the spine. Thus, less trauma may be required to implant the device as compared to the prior art devices noted above, and the patient may therefore feel less pain following surgery and recover more rapidly.
By way of example, the insertion angle may be greater than about 10xc2x0, and more preferably in a range of about 15-30xc2x0 (and even up to about 90xc2x0 for certain surgical techniques). The method may also include removing at least some of a spinal disc between the vertebral bodies prior to positioning. Additionally, the support device may be positioned from the posterior or anterior of the spine.